2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsExpr]{Abstract Haskell syntax: expressions}
9 #include "HsVersions.h"
12 import {-# SOURCE #-} HsMatches ( pprMatches, pprMatch, Match )
14 import HsBinds ( HsBinds )
15 import HsBasic ( HsLit )
16 import BasicTypes ( Fixity(..), FixityDirection(..) )
17 import HsTypes ( HsType )
20 import Name ( Name, NamedThing(..), isLexSym, occNameString )
22 import PprType ( pprType, pprParendType )
23 import Type ( GenType )
24 import Var ( GenTyVar, Id )
25 import DataCon ( DataCon )
26 import SrcLoc ( SrcLoc )
29 %************************************************************************
31 \subsection{Expressions proper}
33 %************************************************************************
36 data HsExpr flexi id pat
37 = HsVar id -- variable
38 | HsLit HsLit -- literal
39 | HsLitOut HsLit -- TRANSLATION
40 (GenType flexi) -- (with its type)
42 | HsLam (Match flexi id pat) -- lambda
43 | HsApp (HsExpr flexi id pat) -- application
46 -- Operator applications:
47 -- NB Bracketed ops such as (+) come out as Vars.
49 -- NB We need an expr for the operator in an OpApp/Section since
50 -- the typechecker may need to apply the operator to a few types.
52 | OpApp (HsExpr flexi id pat) -- left operand
53 (HsExpr flexi id pat) -- operator
54 Fixity -- Renamer adds fixity; bottom until then
55 (HsExpr flexi id pat) -- right operand
57 -- We preserve prefix negation and parenthesis for the precedence parser.
58 -- They are eventually removed by the type checker.
60 | NegApp (HsExpr flexi id pat) -- negated expr
61 (HsExpr flexi id pat) -- the negate id (in a HsVar)
63 | HsPar (HsExpr flexi id pat) -- parenthesised expr
65 | SectionL (HsExpr flexi id pat) -- operand
66 (HsExpr flexi id pat) -- operator
67 | SectionR (HsExpr flexi id pat) -- operator
68 (HsExpr flexi id pat) -- operand
70 | HsCase (HsExpr flexi id pat)
71 [Match flexi id pat] -- must have at least one Match
74 | HsIf (HsExpr flexi id pat) -- predicate
75 (HsExpr flexi id pat) -- then part
76 (HsExpr flexi id pat) -- else part
79 | HsLet (HsBinds flexi id pat) -- let(rec)
83 [Stmt flexi id pat] -- "do":one or more stmts
87 [Stmt flexi id pat] -- "do":one or more stmts
91 (GenType flexi) -- Type of the whole expression
94 | ExplicitList -- syntactic list
96 | ExplicitListOut -- TRANSLATION
97 (GenType flexi) -- Gives type of components of list
100 | ExplicitTuple -- tuple
101 [HsExpr flexi id pat]
102 -- NB: Unit is ExplicitTuple []
103 -- for tuples, we can get the types
104 -- direct from the components
107 | HsCon DataCon -- TRANSLATION; a saturated constructor application
109 [HsExpr flexi id pat]
111 -- Record construction
112 | RecordCon id -- The constructor
113 (HsRecordBinds flexi id pat)
115 | RecordConOut DataCon
116 (HsExpr flexi id pat) -- Data con Id applied to type args
117 (HsRecordBinds flexi id pat)
121 | RecordUpd (HsExpr flexi id pat)
122 (HsRecordBinds flexi id pat)
124 | RecordUpdOut (HsExpr flexi id pat) -- TRANSLATION
125 (GenType flexi) -- Type of *result* record (may differ from
126 -- type of input record)
127 [id] -- Dicts needed for construction
128 (HsRecordBinds flexi id pat)
130 | ExprWithTySig -- signature binding
131 (HsExpr flexi id pat)
133 | ArithSeqIn -- arithmetic sequence
134 (ArithSeqInfo flexi id pat)
136 (HsExpr flexi id pat) -- (typechecked, of course)
137 (ArithSeqInfo flexi id pat)
139 | CCall FAST_STRING -- call into the C world; string is
140 [HsExpr flexi id pat] -- the C function; exprs are the
141 -- arguments to pass.
142 Bool -- True <=> might cause Haskell
143 -- garbage-collection (must generate
144 -- more paranoid code)
145 Bool -- True <=> it's really a "casm"
146 -- NOTE: this CCall is the *boxed*
147 -- version; the desugarer will convert
148 -- it into the unboxed "ccall#".
149 (GenType flexi) -- The result type; will be *bottom*
150 -- until the typechecker gets ahold of it
152 | HsSCC FAST_STRING -- "set cost centre" (_scc_) annotation
153 (HsExpr flexi id pat) -- expr whose cost is to be measured
156 Everything from here on appears only in typechecker output.
159 | TyLam -- TRANSLATION
161 (HsExpr flexi id pat)
162 | TyApp -- TRANSLATION
163 (HsExpr flexi id pat) -- generated by Spec
166 -- DictLam and DictApp are "inverses"
169 (HsExpr flexi id pat)
171 (HsExpr flexi id pat)
174 type HsRecordBinds flexi id pat
175 = [(id, HsExpr flexi id pat, Bool)]
176 -- True <=> source code used "punning",
177 -- i.e. {op1, op2} rather than {op1=e1, op2=e2}
180 A @Dictionary@, unless of length 0 or 1, becomes a tuple. A
181 @ClassDictLam dictvars methods expr@ is, therefore:
183 \ x -> case x of ( dictvars-and-methods-tuple ) -> expr
187 instance (NamedThing id, Outputable id, Outputable pat) =>
188 Outputable (HsExpr flexi id pat) where
189 ppr expr = pprExpr expr
193 pprExpr :: (NamedThing id, Outputable id, Outputable pat)
194 => HsExpr flexi id pat -> SDoc
196 pprExpr e = pprDeeper (ppr_expr e)
197 pprBinds b = pprDeeper (ppr b)
199 ppr_expr (HsVar v) = ppr v
201 ppr_expr (HsLit lit) = ppr lit
202 ppr_expr (HsLitOut lit _) = ppr lit
204 ppr_expr (HsLam match)
205 = hsep [char '\\', nest 2 (pprMatch True match)]
207 ppr_expr expr@(HsApp e1 e2)
208 = let (fun, args) = collect_args expr [] in
209 (ppr_expr fun) <+> (sep (map ppr_expr args))
211 collect_args (HsApp fun arg) args = collect_args fun (arg:args)
212 collect_args fun args = (fun, args)
214 ppr_expr (OpApp e1 op fixity e2)
216 HsVar v -> pp_infixly v
219 pp_e1 = pprParendExpr e1 -- Add parens to make precedence clear
220 pp_e2 = pprParendExpr e2
223 = hang (pprExpr op) 4 (sep [pp_e1, pp_e2])
226 = sep [pp_e1, hsep [pp_v, pp_e2]]
228 pp_v | isLexSym (occNameString (getOccName v)) = ppr v
229 | otherwise = char '`' <> ppr v <> char '`'
231 ppr_expr (NegApp e _)
232 = char '-' <+> pprParendExpr e
234 ppr_expr (HsPar e) = parens (ppr_expr e)
236 ppr_expr (SectionL expr op)
238 HsVar v -> pp_infixly v
241 pp_expr = pprParendExpr expr
243 pp_prefixly = hang (hsep [text " \\ x_ ->", ppr op])
244 4 (hsep [pp_expr, ptext SLIT("x_ )")])
245 pp_infixly v = parens (sep [pp_expr, ppr v])
247 ppr_expr (SectionR op expr)
249 HsVar v -> pp_infixly v
252 pp_expr = pprParendExpr expr
254 pp_prefixly = hang (hsep [text "( \\ x_ ->", ppr op, ptext SLIT("x_")])
255 4 ((<>) pp_expr rparen)
257 = parens (sep [ppr v, pp_expr])
259 ppr_expr (HsCase expr matches _)
260 = sep [ sep [ptext SLIT("case"), nest 4 (pprExpr expr), ptext SLIT("of")],
261 nest 2 (pprMatches (True, empty) matches) ]
263 ppr_expr (HsIf e1 e2 e3 _)
264 = sep [hsep [ptext SLIT("if"), nest 2 (pprExpr e1), ptext SLIT("then")],
269 -- special case: let ... in let ...
270 ppr_expr (HsLet binds expr@(HsLet _ _))
271 = sep [hang (ptext SLIT("let")) 2 (hsep [pprBinds binds, ptext SLIT("in")]),
274 ppr_expr (HsLet binds expr)
275 = sep [hang (ptext SLIT("let")) 2 (pprBinds binds),
276 hang (ptext SLIT("in")) 2 (ppr expr)]
278 ppr_expr (HsDo do_or_list_comp stmts _) = pprDo do_or_list_comp stmts
279 ppr_expr (HsDoOut do_or_list_comp stmts _ _ _ _ _) = pprDo do_or_list_comp stmts
281 ppr_expr (ExplicitList exprs)
282 = brackets (fsep (punctuate comma (map ppr_expr exprs)))
283 ppr_expr (ExplicitListOut ty exprs)
284 = hcat [ brackets (fsep (punctuate comma (map ppr_expr exprs))),
285 ifNotPprForUser ((<>) space (parens (pprType ty))) ]
287 ppr_expr (ExplicitTuple exprs True)
288 = parens (sep (punctuate comma (map ppr_expr exprs)))
290 ppr_expr (ExplicitTuple exprs False)
291 = ptext SLIT("(#") <> sep (punctuate comma (map ppr_expr exprs)) <> ptext SLIT("#)")
293 ppr_expr (HsCon con_id tys args)
294 = ppr con_id <+> sep (map pprParendType tys ++
295 map pprParendExpr args)
297 ppr_expr (RecordCon con_id rbinds)
298 = pp_rbinds (ppr con_id) rbinds
299 ppr_expr (RecordConOut data_con con rbinds)
300 = pp_rbinds (ppr con) rbinds
302 ppr_expr (RecordUpd aexp rbinds)
303 = pp_rbinds (pprParendExpr aexp) rbinds
304 ppr_expr (RecordUpdOut aexp _ _ rbinds)
305 = pp_rbinds (pprParendExpr aexp) rbinds
307 ppr_expr (ExprWithTySig expr sig)
308 = hang (nest 2 (ppr_expr expr) <+> ptext SLIT("::"))
311 ppr_expr (ArithSeqIn info)
312 = brackets (ppr info)
313 ppr_expr (ArithSeqOut expr info)
314 = brackets (ppr info)
316 ppr_expr (CCall fun args _ is_asm result_ty)
318 then ptext SLIT("_casm_ ``") <> ptext fun <> ptext SLIT("''")
319 else ptext SLIT("_ccall_") <+> ptext fun)
320 4 (sep (map pprParendExpr args))
322 ppr_expr (HsSCC label expr)
323 = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ptext label), pprParendExpr expr ]
325 ppr_expr (TyLam tyvars expr)
326 = hang (hsep [ptext SLIT("/\\"), interppSP tyvars, ptext SLIT("->")])
329 ppr_expr (TyApp expr [ty])
330 = hang (ppr_expr expr) 4 (pprParendType ty)
332 ppr_expr (TyApp expr tys)
333 = hang (ppr_expr expr)
334 4 (brackets (interpp'SP tys))
336 ppr_expr (DictLam dictvars expr)
337 = hang (hsep [ptext SLIT("\\{-dict-}"), interppSP dictvars, ptext SLIT("->")])
340 ppr_expr (DictApp expr [dname])
341 = hang (ppr_expr expr) 4 (ppr dname)
343 ppr_expr (DictApp expr dnames)
344 = hang (ppr_expr expr)
345 4 (brackets (interpp'SP dnames))
349 Parenthesize unless very simple:
351 pprParendExpr :: (NamedThing id, Outputable id, Outputable pat)
352 => HsExpr flexi id pat -> SDoc
356 pp_as_was = pprExpr expr
360 HsLitOut l _ -> ppr l
363 ExplicitList _ -> pp_as_was
364 ExplicitListOut _ _ -> pp_as_was
365 ExplicitTuple _ _ -> pp_as_was
368 _ -> parens pp_as_was
371 %************************************************************************
373 \subsection{Record binds}
375 %************************************************************************
378 pp_rbinds :: (NamedThing id, Outputable id, Outputable pat)
380 -> HsRecordBinds flexi id pat -> SDoc
382 pp_rbinds thing rbinds
384 4 (braces (hsep (punctuate comma (map (pp_rbind) rbinds))))
386 pp_rbind (v, e, pun_flag)
387 = getPprStyle $ \ sty ->
388 if pun_flag && userStyle sty then
391 hsep [ppr v, char '=', ppr e]
394 %************************************************************************
396 \subsection{Do stmts and list comprehensions}
398 %************************************************************************
401 data StmtCtxt -- Context of a Stmt
402 = DoStmt -- Do Statment
403 | ListComp -- List comprehension
404 | CaseAlt -- Guard on a case alternative
405 | PatBindRhs -- Guard on a pattern binding
406 | FunRhs Name -- Guard on a function defn for f
407 | LambdaBody -- Body of a lambda abstraction
410 = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts))
413 hang (pprExpr expr <+> char '|')
416 ReturnStmt expr = last stmts -- Last stmt should be a ReturnStmt for list comps
421 data Stmt flexi id pat
423 (HsExpr flexi id pat)
426 | LetStmt (HsBinds flexi id pat)
428 | GuardStmt (HsExpr flexi id pat) -- List comps only
431 | ExprStmt (HsExpr flexi id pat) -- Do stmts; and guarded things at the end
434 | ReturnStmt (HsExpr flexi id pat) -- List comps only, at the end
438 instance (NamedThing id, Outputable id, Outputable pat) =>
439 Outputable (Stmt flexi id pat) where
440 ppr stmt = pprStmt stmt
442 pprStmt (BindStmt pat expr _)
443 = hsep [ppr pat, ptext SLIT("<-"), ppr expr]
444 pprStmt (LetStmt binds)
445 = hsep [ptext SLIT("let"), pprBinds binds]
446 pprStmt (ExprStmt expr _)
448 pprStmt (GuardStmt expr _)
450 pprStmt (ReturnStmt expr)
451 = hsep [ptext SLIT("return"), ppr expr]
454 %************************************************************************
456 \subsection{Enumerations and list comprehensions}
458 %************************************************************************
461 data ArithSeqInfo flexi id pat
462 = From (HsExpr flexi id pat)
463 | FromThen (HsExpr flexi id pat)
464 (HsExpr flexi id pat)
465 | FromTo (HsExpr flexi id pat)
466 (HsExpr flexi id pat)
467 | FromThenTo (HsExpr flexi id pat)
468 (HsExpr flexi id pat)
469 (HsExpr flexi id pat)
473 instance (NamedThing id, Outputable id, Outputable pat) =>
474 Outputable (ArithSeqInfo flexi id pat) where
475 ppr (From e1) = hcat [ppr e1, pp_dotdot]
476 ppr (FromThen e1 e2) = hcat [ppr e1, comma, space, ppr e2, pp_dotdot]
477 ppr (FromTo e1 e3) = hcat [ppr e1, pp_dotdot, ppr e3]
478 ppr (FromThenTo e1 e2 e3)
479 = hcat [ppr e1, comma, space, ppr e2, pp_dotdot, ppr e3]
481 pp_dotdot = ptext SLIT(" .. ")